Advance Deposit Account - A debit account into which a mailer deposits funds that are maintained by the USPS and from which postage is later deducted at the time of mailing. (Also called trust account.)
Automation–Compatible Mail - Mail that is prepared according to USPS standards so it can be scanned and processed by automated mail processing equipment such as a barcode sorter.

Balloon Price - A price charged for Priority Mail (for delivery to Zones 1-4) and Standard Post items that weigh less than 20 pounds but measure more than 84 inches but no more than 108 inches in combined length and girth.

Bulk Mail - The term is generally used to describe commercial mail. The term "bulk mail" refers to specific minimum quantities of mail that are prepared as a specific class of mail at reduced postage. For instance, First-Class Mail requires a minimum of 500 pieces for each mailing. Standard Mail requires 200 pieces or 50 pounds for each mailing. The term "bulk mail" is synonymous with commercial, business, or advertising mail.

Business Mail Entry Unit (BMEU) - The area of a postal facility where mailers present bulk and permit mail for acceptance. The BMEU includes dedicated platform space, office space, and a staging area on the workroom floor.

Carrier Route Mail - Mail sorted by carrier route. The mail requires no primary or secondary distribution. The term is a general descriptor of the available prices for this type of preparation, which includes carrier route Standard Mail, carrier route Periodicals, and carrier route Bound Printed Matter.

Commercial Base - A pricing category for Priority Mail Express and Priority Mail that is less than the single-piece price paid at retail, and that requires specific postage payment methods other than postage stamps. Payment methods depend on the class of mail and may include Click-N-Ship, registered end-users of USPS-approved PC Postage providers, or customers using IBI postage meters that electronically transmit transactional data to the USPS.

Commercial Plus - A pricing category for Priority Mail Express and Priority Mail that is less than Commercial Base pricing, and that requires specific postage payment methods and annual volume requirements.

Destination Entry Discount - A postage discount for depositing mail at specific postal facilities (e.g., delivery unit or network distribution center) that are closer to the final destination of the mail.

Full Letter Tray - A tray filled at least 85% full with faced, upright pieces. Each tray must be physically filled to capacity before the filling of the next tray. A tray with less mail may be prepared only if less–than–full or overflow trays are permitted by the standards for the price claimed. (Also see less–than–full tray and overflow tray).

Known Office of Publication - The business office of a Periodicals publication that is in the city where the original entry for Periodicals mailing privileges is authorized.

Mailing Permit - Permission to mail at commercial (presorted) prices.

Meter Tape - A piece of adhesive paper that is fed through a postage meter and imprinted with postage. The meter tape is then applied to a mailpiece (usually a large envelope or parcel that is too big to fit through the postage meter).

Nonmachinable - First-Class Mail letters that are square, rigid or have one or more nonmachinable characteristics are subject to the nonmachinable surcharge. Standard Mail letters with nonmachinable characteristics are subject to nonmachinable prices. Parcel Select packages that cannot be sorted on mail processing equipment because of size or weight must be processed manually and are nonmachinable.

Oversized Price - Standard Post price for pieces exceeding 108 inches but not more than 130 inches in combined length and girth.

Postage Meter - A device that can print one or more denominations of postage onto a mailpiece or meter tape. It is available for lease only from designated manufacturers.

PC Postage - Approved third-party vendor software that mailers can use to pay for and print their postage using a computer, printer, and internet connection.

Presort - The process by which a mailer prepares mail so that it is sorted to the finest extent required by the standards for the price claimed. Generally, presort is performed sequentially, from the lowest (finest) level to the highest level, to those destinations specified by standard and is completed at each level before the next level is prepared. Not all presort levels are applicable to all mailings.

Presorted First-Class Mail - A nonautomation category for a mailing that consists of at least 500 addressed mailpieces and is sorted and prepared according to USPS standards. This mail may bear a barcode.
Presorted Mail - A form of mail preparation, required to bypass certain postal operations, in which the mailer groups pieces in a mailing by ZIP Code or by carrier route or carrier walk sequence (or other USPS–recommended separation).
Presorted Prices - Prices which are lower than single-piece prices. In exchange for this lower postage price, mailers must sort their mail into containers based on the ZIP Code destinations on the mail.

Sectional Center Facility (SCF) - A postal facility that serves as the processing and distribution center (P&DC) for Post Offices in a designated geographic area as defined by the first three digits of the ZIP Codes of those offices. Some SCFs serve more than one 3–digit ZIP Code range.
Single-Piece - The "retail" or "full" postage price available for individual pieces of Priority Mail Express, First-Class Mail, Priority Mail, and Package Services. Single-piece prices are higher than prices available for commercial mail.
Sort - To separate mail by a scheme or ZIP Code range; to separate and place mail into a carrier case; to distribute mail by piece, package, bundle, sack, or pouch. (Also see primary, secondary, and tertiary.)

Sortation - The distribution or separation of mail to route it to its final delivery point.

USPS Tracking - Is an extra service that can be optionally purchased by mailers to have their mailpiece scanned at delivery. USPS Tracking is available for Priority Mail, First-Class Mail parcels, Standard Mail machinable or irregular parcels, Package Services, and Parcel Select packages. Extra services fees are in addition to postage.

Weighted Fee - The fee charged the sender for Standard Mail pieces endorsed "Address Service Requested" or "Forwarding Service Requested" that are returned as undeliverable. The fee equals the single-piece First-Class Mail price multiplied by a factor of 2.472, rounded to the next whole cent.